Timing device



Nov. '3, 1942.

W. G. LASKEY TIMING DEVICE Filed Oct. 4, 1939 2 Sheets-Sheet l BV wem ATTORNEY Nov. 3, 1942. w, G, LASKEY TIMING DEVICE Filed ocx. 4, 1959 2 Sheets-Sheet 2 Patented 3%, 194

'rnmNG DEVICE William G. Laskey, Schooleys Mountain, N. 3., assignor to Bell Telephone Laboratories, Incorporated. New York, N. Y., a corporation o! New York Application October 4, 1939, Serial No. 297,883

14 Claims.

invention relates to timing devices and particularly to mechanisms for registering the passage of time.

An object of this invention is to improve such devices to accurately and reliably measure and register the passage of time Heretofore mechanisms of this type have been provided including balance wheel or pendulum operated devices for measuring of time intervals in which various means were provided for regulating the action of the lbalance wheel or pendu- A lum to register the time intervals. For such mechanisms energy was directly or indirectly applied to start the balance wheel or pendulum and keep it in operation, and regulate its action and clockworks were employed for indicating the time intervals.-

It is a feature of the present invention to provide a mechanism of this general type inwhich the operation may be started at will, continued and stopped at the end of accurately iixed periods of time and to control an indicating signal at the end of this period. The mechanism consists of a balance means, a magnet, levers and circuit means cooperating to start the balance means to oscillate and to maintain its osciilation at its natural frequency under control of energy stored in a spring by the H et. It also includes a step-by-sten 'mechanism lcontrolled by the lever means, a

means for stopping said mechanism when a certain number of steps have been taken, and means for then operating a signal. 'llhe invention has been illustrated in the accompanying drawings in which Fig. i shows a top view oi a mechanism embodying the applicants invention;

Fig. 2 shows a left-hand side view of this mechanism;

Fig. 3 shows a iront view of this mechanism;

y' Fig. 4 shows a detail of the mechanism;

Figs. 5, 6, 7 and 8 show various positions oi the oscillating lever mechanism to illustrate the actions thereof: and,

Fig. 9 is a diagrammatic drawing of the circuit elements involved in this mechanism.

Referring now to the drawings and particularly to Figs. 1 to 4, the mechanism may cony veniently be divided, for the sake of clearness in describing it in two groups of parts, to wit, an oscillating mechanism which has practically all of its parts located below the mounting plate i and a. signal operating mechanism which is located above this plate.

The oscillating mechanism is mounted between the plates i and 2 and consists of a balance Wheel 3 mounted on a shaft t which is journaled in bearings located respectively in plates l and 2 as clearly shown in Fig, 3. This balance wheel may be oscillated by a spiral poses as `will be described hereinafter.

spring 5 which has its inner end connected to the shaft t and its outer end connected to a post 6 secured to plate 2. The plates i and 2 are held together by four posts, l, 8, 9 and 10. On the shaft 4 is also located a. hub il having a pin I2 which is operated upon as will be hereinafter described to start the balance wheel to oscillate and to maintain it in oscillation. On the upper flat surface of balance wheel 3 is also located a hub or post i3 in which is secured 'a tripping member i4 shown more in detail, for example, in Fig. 6, mounted under control of a spring I5 to yieldingly turn in a counter-clockwise direction looking at Fig. 6 but hel'd in an unyielding normal position by the spring l5 in the post i3 as far as movement of this member is concerned in a clockwise direction. The purpose of this member will be described hereinafter. Below plate i looking at Fig. l is mounted a solenoid coil i8 in a bracket it secured to plate i. This solenoid coil operates on a plunger 2t to move it from a normal position as shown in Fig. 5 to a position where the buffer bushing 2i on the plunger 2li touches the left-hand spoolhead of the solenoid coil it. This plunger it is provided with a bushing 22 on a buer bushing 23 to operate a lever 2d against the tension of a spring 25 for pur- This lever 2d is mounted on a shaft 2t which is journaled at its lower end in a bearing on a supporting plate 2i, secured between posts 'ZI and t as shown in Figs. 2 and 3 in. particular, and protrudes through a bearing in plate i above this plate. Secured to this shaft 2t is also a trigger di which may be engaged by a strip lever 32 mounted rotatably in one direction against the tension of a spring 33 on a bushing or bearv ing post 3d which is secured to the plate il as shown clearly in Figs. 3, 6, 7 and 8. The purpose of thispartcular lever is to hold the lever 2d in operated position when it has been moved by the plunger 2t against the tension of spring 2t. Secured to shaft 2t is also an operating lever 3@ which is shaped at its free end in the form of a U and terminates into a. shank or projection 3l which may engage pin i2 to start and maintain the oscillation oi the balance wheel t. Mounted loosely on shaft 2t is also another lever mechanism 39 which is provided with a stop screw MB that may engage or be engaged by lever it during the operation of the mechanism. The lever mechanism 39 is also provided with a shank or extension 42 having'a latchprojection d3 that may be engaged by a latch hook it mounted on a shaft 435 secured in a bracket d6 which in turn is secured to plate i as shown particularly in Figs. 2 and 3. This latch hook M is held in the normal position as shown in Fig. 5 by a helical spring it to latch the lever mechanism 39 in this normal position by engaging the projection t3,

The arm 42 also extends at an oblique angle outwardly to terminate in an insulation bushing 41 that normally holds the operating springs 49 closed. These operating springs 49 are mounted on a bracket secured to plate I. Each time th'e plunger 20 is operated it is evident that shaft 26 will be rotated and when the plunger is released it will be returned to normal position. Thus shaft 26 will oscillate back and forth during the operation of the mechanism as will hereratchet Wheel 56 mounted on a shaft 51 which in turn is rotatably mounted in a bearing on plate I and in a bearing in a bracket 59. This ratchet wheel 56 may be held in a normal position by a helical spring 60, one end of which is secured to plate I and the other to the ratchet wheel hub 6I by means of which the ratchet wheel is connected to the shaft'51. This normal position of the ratchet wheel is determined by a pin 63 on this wheel which engages a projection 64 on the bracket 59. Above the bracket 59 on shaft 51 is mounted a disc 65 which as shown in Figs. 1 and 4 is provided with an indentation 61 and below this indentation is mounted a iiexible spring 66 which may be moved in any desired position in the indented portion 61 of disc 65 to form a downwardly slanting end 69 at any desired radial position. This spring 6B may be engaged on its outer edge by the hooked shaped end of spring 10, if the disc is rotated in anti-clockwise direction looking at Fig. 1, and after it has been rotated a certain distance as determined by the location oi the slanting end 69 the hooked shaped end of spring 10 will be disengaged from the spring 66 as shown in Fig. 4. Thus the rotation of this disc 65 by the ratchet wheel as controlled by the pawl 51 will cause the hooked shaped end of spring 10 after a certain number of steps have been taken to enter the indentation 61. When this takes place, the spring 10 will be moved inwardly looking at Fig. 1 to cause bushing 12 thereon to close a connection between springs 13 and to open the connection between springs 14, the purpose of which will be described hereinafter. These springs 13, 14 and 10 are all mounted on a bracket 15 connected to plate I. The downwardly slanting end 69 on spring 68 permits the spring 10 to return to normal position when the ratchet wheel is returned to normal as the hook shaped end will slide over the slanting end 69 and be engaged by the wheel 65 as it passes out of the indentation 61. On bracket 15 is also mounted a relaystructure 16 having an armature 11, which when attracted by the energization of the relay coil 1.6 is moved downwardly, looking at Fig. 1, to cause the spring 18 which is provided with a pawl shaped end to engage a tooth in the ratchet wheel 56 and thus serves as a holding pawl for the ratchet wheel When operated. This armature 11 also operates to close a connection between the springs 19 when actuated. Springs 19 and 18 as Well as armature 11 are mounted at the rear of the relay structure on projections 80 on the core of the relay which is mounted The operation of the oscillating and signal operating mechanism will now be described in connection particularly with Figs. 5 to 9. To start the oscillating mechanism to measure the passage of time a key IUI) as shown in Fig. 9 may be closed. The operation of this key closes a circuit for relay 16 from battery through the winding of thisjrelay, contacts of key |00 back to battery. The operation of relay 16 causes the armature 11 to bring the pawl 18 in contact with a tooth in the ratchet wheel 56 to serve as a holding pawl and closes a connection between the contacts 19. This in turn causes a circuit to be closed 'for the operation of the solenoid coil Il from battery through this coil, contacts 4l, 14 and 19 back to battery. The solenoid I6 now operates and .attracts the plunger 20 towards the right, looking at Fig. 5 to operate the lever 24 to store energy in spring 25 and to rotate shaft 26. When the solenoid has attracted the plunger 20 to the point where the bushing 2| touches the left-hand spoolhead of the solenoid, the trigger 3| will be locked by the trip lever 32 as shown in Figs. 6 and '7. The normal positionsoi lever 24 and the operating lever 36A are shown in Fig. 5 and when operated the lever 36 will be drawn downwardly to the position shown in Figs. 6 and '1 and thus the projection 31 on its inner side will hit the pin I2 on the upper side and cause the balance Wheel 3 to be rotated in a clockwise direction and store energy in spring 5. The position of the balance wheel 3, after it has been rotated in this direction, is indicated in Fig. 6. It will be noted that tripping member I4 is located directly above the shaft 4 and this indicates the limits of the travel of the balance wheel in the clockwise direction as controlled by the projection 31. at this time. When the lever 38 reaches this position as shown in Fig. 6, lt will operate on catch hook 44 to cause it to unlatch itself from the latch projection 43 on the extension 42 which is then moved into the position as shown in Fig. 6 under tension of the springs 43 which are now opened. This, of course, opens the circuit for the solenoid coil I8 which deenergizes and the plunger 20 is now free to return 'to normal although it will not be returned until .lever 24 pushes it back to the normal position.

The balance wheel 3 Will now start to rotate back under tension of spring 5 in a counter-clockwise direction until the tripping member I4 strikes the trip lever 32 as shown in Fig. 7 and the member I4 will therefore by continuing further in this direction cause lever 32 to release the trigger 3I which in turn causes the levers 24 and 36 to be returned to normal position under tension of spring 25. It should be noted at this time that pin I2 will be in a position where it will be hit through other projections BI on the brackets 15.

on the under side by'the projection 31 on the upper side on the return of the lever 36 to normal and thus the balance wheel will receive an additional impulse to continue to rotate in the counter-clockwise direction for a short distance to store energy in the spring 5 in the opposite direction. Fig. 8 shows the position of the parts mentioned after the projection 31 has struck pin I2 and the pin is about to leave the projection. The balance wheel rotates in this direction for a certain distance and the tension in the spring 5 will then cause it to be rotated back in a clockwise direction. As the member I4 now passes the trip lever 32 it will merely yield and pass by this lever 32 and cause no operations to take place at this time. The balance wheel will continue to rotate in the clockwise direction until energy has been stored in spring 5 in the opposite direction. It should be noted that on the return of lever 36 to normal position it will strike the stop screw 40 on the lever mechanism 39 and thus cause this lever mechanism to be rotated in a counter-clockwise direction to cause the latch projection 43 to be latched Aby the hook 44. VThe connection between the springs 48 will therefore now be restored. As the circuit for the solenoid I8 is now closed the levers 24 and 36 will again vbe operated to take the position shown in Figs. 6 and 7 and when the balance Wheel starts to return in the counter-clockwise direction, the member I4 will again operate on the lever 32 to unlatch the trigger 3| and the projection 31 on lever 3G Will again deliver an operating stroke to the pin I2 to causeA the balance wheel to continue in the counter-clockwise direction to store energy in the spring 5. The operations are then repeated as described and consequently thev` operation of the solenoid IB causes the shaft 26 to be rotated in one direction and the release of the lever 24 under tension of the spring 25 causes the shaft 26 to be rotated in the opposite direction. As determined by the mass of the balance wheel t, the tension of the spring 5, the energy stored in spring 25 and the consequent force of the blow that the projection 3l delivers to the pin i2 the balance wheel will continue to oscillate at a uniform and accurately determined frequency, that is, if these factors are properly adjusted, the shaft 2t will be oscillated back and forth at an extremely, accurate rate. The force of the blow delivered by the projection 3i will always be the same' as it is determined by the energy stored in sprlnfg 25 and is not dependent on any variations in the current that actuates the plunger 2t. A very accurate measuring means of the passage of time is therefore obtained by this oscillating mechanism.

The effect of the oscillations of the shaft 2S on the signal operating mechanism will now be described. For each forward or clockwise movement of the disc ti', the pawl 5t will engage a tooth in the ratchetvwheel t6 and cause it to be stepped one step or the equivalent of one tooth and the ratchet wheel will be held in the operated position by the holding pawl it. This rotation of the ratchet wheel will continue until the hook shaped end of the member it passes over the slanting end @t of the member td and takes the position shown in Fig. 4 when this member will press inward towards the center of disc E5. When the spring it is thus operated contacts i4 will be opened and I3 will be closed. The circuit for the solenoid it is now opened by the contacts 'itl and prevent the levers 2t and Bt from being further operated by the' plunger 2t. The contacts F3 close an obvious circuit for the lighting oi' the lamp iili to indicate that a definite time interval has elapsed since the closure of key it. The mechanismsnowrei'nain in this position until reset by the release of the key i0@ which releases magnet i6, which in turn releases lthe holding pawllil. This causes the ratchet wheel to return to normal under the tension of the spring 60 and the arm It will be pushed out of its operated position due to the fact that it will engage the slanting end 69 and be restored to normal by riding up and out of the indentation 61 on disk 65. This in turn causes the closure of contacts 14 and the opening of contacts 'i3 causing the extinction of the lamp IIN. A measurement of the same interval of time may be repeated each different periods of time may be measured by this apparatus by merely shifting the spring B8 to different positions on the disc 65 so that diiierent numbers of steps may be taken by the ratchet wheel before the signal is operated and that the key |00 may start the apparatus moving automatically without setting the balance Wheel in motion manually,

What is claimed is:

1. In a signal operating system, a signal, a balance means, a magnet, an armature for said magnet, circuit means for causing said magnet to be energized to attract vsaid armature, means controlled by said armature for starting said balance mean's to oscillate during the attractive operation of said armature, a lever mechanism cooperating with said armature through said means controlled thereby, cooperating with said circuit means and with said balance means during succeeding attractive operations of said armature to maintain said balance means in oscillation at its natural frequency under control of said armature, a shaft controlled by said armature to oscillate at the same frequency as the balance means, a ratchet time the key Inn is operated, It is evident that mechanism controlled by the oscillation of said shaft to operate in a step-by-step manner to take one step for each oscillation of the shaft, means controlled by said ratchet mechanism when it has taken a certain number of steps ior discontinuing to maintain said balance means and said shaft in oscillation, and means operated by said 1ast-mentioned means when the ratchet mechanism has stopped operating for actuating said signal,

2. In a signal operating mechanism, a signal, a mechanism for measuring the passage of time comprising an oscillating device, operating means comprising a single magnet, an armature therefor, circuit means and a lever mechanism for starting said oscillating device to oscillate and i'or maintaining said oscillating device in oscillation at its natural frequency, manually operated means for starting said operating means, counting means controlled by said oscillating device to count the oscillations of said oscillating device, means operative by said counting means when it has operated a definite number of times for stopping the oscillating device and for actuating said signal,

3. In a signal operating system, a signal, a

balance wheel, operating means comprising a single magnet, an armature therefor, circuit means and a lever mechanism for starting said balance Wheel to oscillate and for maintaining said balance Wheel in oscillation at its natural frequency, manual means for starting said operating means, a'ratchet mechanism operative to take one step for each oscillation of said wheel, means controlled by said ratchet mechanism for stopping said operating means after the balance Wheel has completed a certain number of oscillations and for thereafter actuating said signal. 4. In a signal operating system, a signal, a mechanism for measuring the passage of time, operating means comprising a. single magnet, an armature therefor, circuit means and a lever mechanism for startingsaid time measuring mechanism to function and for maintaining its function at a constant rate, a ratchet mechanism operative to take steps at a rate controlled by said operating means, and means controlled by said ratchet mechanism when it has taken a certain number of steps for disabling said operating means and lactuating said signal.

5. Ina signal operating system, a signal, a

mechanism for starting said time measuring mechanism to function and for maintaining its function at a constant rate, manually operative means for starting said operating means to funcv tion, a ratchet mechanism operative to take steps at a rate controlled by said first-mentioned operating means, and means controlled by said ratchet mechanism when it has taken a certain number oil steps for stopping the iunction oi said first-mentioned operating means and for actuating said signal.

c. In a signal operatina system. a signal. a balance wheel, a magnet, an armature for said magnet, a spring for said armature, a lever mechf anism, said balance wheel, magnet. armature, spring and lever mechanism being so arranged that said amature when nrst attracted by said magnet starts said balance wheel to oscillate and said armature stores a certain amount of energy in said spring each time said armature is attracted and so that said spring inturn delivers said certain amounts of energy through said armature and said lever mechanism to said balance wheel each time said amature is released to cause said balance wheel to oscillate at its natural frequency, a ratchet mechanism controlled by said amature to take one step for each oscillation of said armature and means controlled by said ratchet-mechanism when it has taken a certain number of steps for discontinuing said cooperative function of said balance wheel, lever mechanism, magnet, armature and spring and for operating said signal.

7. In a time measuring device, a signal, a mechanism for measuring the passage of time comprising a balance wheel, a spring for controlling the oscillations of said wheel, a switch, a circuit controlled by said switch, a relay in said circuit operative when said circuit is closed, a second circuit closed by said relay when operated, a magnet in said second circuit operative when said second circuit isV closed, a lever operated from a normal to an actuated position when said magnet is energized, means for locking said lever in its actuated position, a spring controlled by said lever to store energy when said lever` is operated to its actuated position, means controlled by said lever when nrst operated to actuated position tp start the wheel to oscillate and controlled by said lever each time it is subsequently released to normal under tension of said spring for continuing the oscillations of said wheel, contacts in sai'd second circuit, -a second lever for closing and opening said contacts, a third lever for locking said second lever in its contact closing position; means operative by said ilrst lever in actuated position for causing said third lever to, unlock said second lever for the operation of said conitacts thereby, means operative each time said wheel has oscillated once for actuating said locking means for the first lever to release said lever from the actuated position, means operative by said first lever when released for actuating said second lever to close said contacts and to cause said second lever to be locked by said third lever, and means controlled by said mechanism when it has operated a certain interval of time for stopping its operation and for then operating said signal.

8. In a time measuring device, a signal, a mec anism for measuring the passage of time comprissaid second circuit operative when said second circuit is closed. a lever operated from a normal to an actuated position when said magnet is energized, means for locking said lever in actuated position, a spring controlled by said lever to store energy when said llever is operated .to its actuated position, means controlled by said lever when drst operated to actuated position to start the wheel to oscillate and controlled by said lever each time it is subsequently released to normal under tension of said spring for continuing the oscillations of said wheel, contacts in said second circuit, a

second lever for closing and opening said contacts, a third lever for locking said second lever in its contact closingposition, means operative by said first lever in actuated position for causing said third lever to unlock said second lever for the operation of said contacts thereby. means operative each time said wheel has oscillated once for actuating said locking means for the first lever to release said first lever from the actuated position, means operative by said rst lever when released for actuating said second lever to close said contacts and to cause said second lever to be locked by said third lever, a second mechanism controlled by said ilrst mechanism when it has operated a certain interval of time for stopping its operations comprising a ratchet wheel, pawl mechanism operative each time said rst lever is released for causing said ratchet wheel to take one step, a holding pawl for said ratchet wheel operative to hold said ratchet wheel in an actuated position when said relay is operated, a wheel having a detent therein and attached to said ratchet wheel, a lever normally resting against the edge of said last-mentioned wheel and so arranged that it operates to an actuated position when the wheel has rotated to a position where the lever drops into said detent, means actuated by the last-mentioned lever when it is in operated position for opening said second circuit to stop the first-mentioned mechanism and for actuating said signal.

9. In a signal operating system, a signal, a balance means, a magnet, an armature therefor, circuit means for actuating said magnet to attract said armature, means controlled directly by said armature when ilrst attracted by said magnet for starting said balance means to oscillate, a lever mechanism cooperating with said armature, said circuit means and said balance means when started for controlling said circuit means to alternately release and aotuate said magnet at the natural frequency of oscillations of said balance means to control said balance means and to continue to oscillate at its natural frequency, a shaft controlled by said armature to oscillate at the same frequency as the balance means, Aa ratchet mechanism controlled by the oscillations of said shaft to operate in a step-by-step manner to take one step for each oscillation of the shaft, means controlled by said ratchet mechanism when it has taken a certain number of steps for discontinuing the oscillatory movements of said balance means, said shaft and said ratchet mechanism, and means operated by said last-mentioned means when the ratchet mechanism stops for actuating said signal.

10. In a signal operating mechanism, a signal, a mechanism for measuring the'passagc of time ing a balanced wheel, a spring for controlling the comprising an oscillatory device, a magnet. an

amature therefor, circuit meansfor actuating said magnet to attract said armature, means controlled directly by said armature when first attracted by said magnet for starting said device to oscillate, a lever mechanism cooperating with' said armature, said circuit means and said device when started for controlling said circuit means to alternately release and actuate said magnet at the natural frequency of oscillations of said device to control said device to continue to oscillate at its natural frequency, a relay for controlling said circuit means, manually operative means for actuating said relay for closing said circuit means, counting means controlled by said amature for automatically counting the oscillations of said oscillatory device, and means operative by said counting device when it has operated a certain number of times for opening said circuit means to stop the oscillatory device and for actuating said signal.

11. In a signal operating mechanism, a signal, a balance means, a magnet, an armature for said magnet, a spring for returning said armature to normal position after it has been attracted by n said magnet, means cooperating with said armature and said balance means to start said balance means to oscillate on the first attractive movement of said armature and to maintain said balance means in oscillation at its natural frequency under control of said spring, each time the armature is released, a circuit for energizing said magnet, means controlled by said balance means when oscillating and by said means cooperating with said armature for opening and closing said circuit to regulate the energizing and deenergizing of said magnet to take place once for each cycle of oscillationsy of said balance means, a mechanism controlled lby said armature for opening said circuit after a certain number of operations of said armature and for thereafter actuating said signal.

12. In a signal operating system, a signal, a balance means, a magnet, an armature for said magnet a member associated with said armature to partake of the movements thereof, a spring for returning said armature and member to normal position after the armature has been actuated by said magnet, an extension on said member cooperating with said balance means to maintain said balance means in oscillation at its natural frequency when said armature is released under control of the energy stored in said spring when the armature was attracted by the magnet, a circuit for energizing said magnet, a lever mechanism controlled by said member for opening said circuit when the armature has been attracted by said magnet and for closing said circuit when the armature is released, a lever mechanism for locking said member in its actuated position, means for actuating said last-mentioned lever mechanism to unlock said member controlled by said balance means once for each cycle of oscillation of said balance means, a shaft controlled by said member to oscillate at the same frequency as said member, a ratchet mechanism controlled by the oscillations of said shaft to operate in a step-bystep manner to take one step for each oscillation .of the shaft, means controlled by said ratchet mechanism when it has taken a certain number of steps for opening the circuit for said magnet to discontinue the control by its armature over said ture mechanism to normal after it has been actuated by 'said magnet, means for locking saidarmature mechanism in actuated position, a lever mechanism controlled by said armature mechanism and said balance wheel so arranged that each time the magnet is energized and attracts this armature mechanism, the circuit is broken and when the magnet is deenergized the circuit is closed and so that on the rst energization vof the magnet the armature mechanism starts the balance wheel to oscillate and on subsequent releases of the magnet the armature mechanism maintains the balance wheel in oscillation at its natural frequency by expending the energy stored in the spring and so that the armature mechanism is released =from said locking means under the control of said balance wheel for each cycle of oscillations of the balance wheel, and a mechanism` controlled by theoscillation of said armature mechanism after it has oscillated a certain number of times for opening said circuit permanently to stop the balance wheel and the operations of said magnet, armature and lever mechanism and to actuate said signal.

14. In a signal operating system, a signal, a balance wheel, a magnet, an energizing circuit for said magnet, an armature for said magnet, a lever arranged to oscillate with the armature, a spring for returning said armature and lever to normal after the armature has been attracted and released by said magnet, means controlled by the movement of said lever to actuated position when said magnet is rst energized by said circuit for starting said balance wheel to oscillate, for locking said lever in actuated position and for opening the energizing circuit for said magnet and maintaining said energizing circuit locked in the open condition, means controlled by the oscillatory movement of said balance Wheel for unlocking said lever to permit it to return to normal under tension of said spring, means on said lever and said balance wheel operative when the lever returns to normal for imparting to said wheel an impulse of energy to cause it to continue to oscillate, the energy being derived from the energy stored in the spring when the armature was attracted by said magnet, means controlled by said lever when it returns to normal for unlocking the circuit opening means to close said circuit to permit the repeated energizing and deenergizing of said magnet at a rate determined by the natural oscillatory frequency of the balance wheel, a cam mechanism, means controlled by the repeated operation and release of said lever for actuating said cam mechanism one step for each operation of the armature, means controlled by said cam mechanism when a certain number of steps have been taken for actuating said signal and for opening said circuit to permanently stop the energzation and deenergization of the magnet and stop the oscillations of said wheel.

WILLIAM G. LASKEY. 

